1. Field of the Invention
Embodiments of the present invention relate generally to multi-threaded processing and, more particularly, to a scoreboard system and method for multi-threaded processing.
2. Description of the Related Art
Scoreboards have been used in scalar processing to keep track of registers that are busy so that instructions that need to use these registers can be prevented from being issued during the time these registers are in the busy state. A conventional scoreboard maintains a bit mask for each of the registers that are in a register file. When the bit mask is 1, this indicates that the associated register is busy and instructions that need to use this register should not be issued. When the bit mask is 0, this indicates that the associated register is not busy and instructions that need to use this register can be issued. Therefore, before any instruction can be issued, the scoreboard is checked to see if any of the registers specified in the instruction is busy or not. If none are indicated by the scoreboard as being busy, the instruction is allowed to issue.
The scoreboarding technique described above works adequately for small register files. When the number of registers in the register file becomes very large, however, the size of the scoreboard becomes proportionately large and table look-ups performed on the scoreboard to check if a particular register is busy or not become highly inefficient. As a result, scoreboard checks and updates using the above technique are often too slow to be able to support highly parallel processing architectures that execute a large number of independent threads in parallel.